Officials in Bulgaria are blaming a suicide bomber for an attack on a bus of Israeli tourists that left at least seven people dead and say they are working with U.S. law-enforcement and intelligence services to determine who was responsible.

The attack took place outside the airport in the Black Sea resort city of Burgas after a planeload of Israeli tourists from Tel Aviv had boarded a double-decker bus.

The Bulgarian Interior Ministry says five Israelis were killed in the blast and dozens more injured. The number of Israeli fatalities had been revised down from six.

The Bulgarian bus driver was also killed, along with the bomber, who was reported to be holding what appeared to be a falsified driver's license from the U.S. state of Michigan.

A commentary posted on the website of Iran's state television channel called the Israeli claim "ridiculous."

The Burgas blast is the deadliest attack on Israeli citizens abroad since 2004, when 12 Israelis were killed in a bomb attack in Egypt's Sinai Peninsula.

The blast also came on the 18th anniversary of the 1994 bombing of a Jewish community center in Argentina that killed 85 people. Iranian officials and Hizbollah have been implicated in some official investigations of the attack -- allegations denied by Tehran.

International Investigation

Speaking on July 19, Bulgarian Prime Minister Boiko Borisov said work was under way to indentify the suspected Burgas bomber, whose body is reported to have suffered extensive damage.

"We have strong evidence to believe that [attack] was the work of a suicide bomber," Borisov told reporters. "We've been working closely with our FBI and CIA colleagues and no information was found about the [alleged perpetrator] in their databases. So, we can say with certainty that one of the victims had false [ID] documents."

Bulgaria's Interior Ministry has released a short clip of security camera video showing the man suspected of carrying out the bombing.